Strong Field-Induced Frequency Conversion of Laser Radiation in Plasma Plumes: Recent Achievements

New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications

Nonlinear optical sensors on metal nanoparticles synthesized by ion implantation

Recent results on ion synthesis and nonlinear optical properties of metal nanoparticles in various dielectrics are presented. Copper and silver nanoparticles were fabricated in silica and soda lime glasses by low energy ion implantation. The nonlinear optical characteristics of nanoparticle composite materials, which may be suited for optical sensing, were studied by applying Z-scan transmittance measurements. They were performed in the near IR area at a wavelength of 1,064 nm, using picosecond pulses of a Nd:YAG laser. Optical nonlinearities of the metal nanoparticles in various substrates such as a nonlinear refraction and a nonlinear susceptibility were detected. It was shown that the influence of the dielectric environment (optical constants) around these nanoparticles considerably changes the nonlinear optical response of the composite materials. Ultrafast optical sensors based on nonlinear effects in metal nanoparticles are discussed. © 2011 Springer Science+Business Media B.V

Application of Ion Implantation for Synthesis of Copper Nanoparticles in a Zinc Oxide Matrix for Obtaining New Nonlinear Optical Materials

We have obtained a layered composite material by implantation of single crystal zinc oxide (ZnO) substrates with 160-keV Cu+ ions to a dose of 10(16) or 10(17) cm(-2). The composite was studied by linear optical absorption spectroscopy; the nonlinear optical characteristics were determined by means of Z-scanning at a laser radiation wavelength of 532 nm. The appearance of the optical plasmon resonance bands in the spectra indicated that ion implantation to the higher dose provides for the formation of copper nanoparticles in a subsurface layer of ZnO. The new nonlinear optical material comprising metal nanoparticles in a ZnO matrix exhibits the phenomenon of self-defocusing and possesses a high nonlinear absorption coefficient (beta = 2.07 x 10(-3) cm/W). (C) 2004 MAIK "Nauka / Interperiodica"

Precision Measurements of d(d,p)t and d(d,n)^3He Total Cross Sections at Big-Bang Nucleosynthesis Energies

Recent Wilkinson Microwave Anisotropy Probe (WMAP) measurements have determined the baryon density of the Universe $\Omega_b$ with a precision of about 4%. With $\Omega_b$ tightly constrained, comparisons of Big Bang Nucleosynthesis (BBN) abundance predictions to primordial abundance observations can be made and used to test BBN models and/or to further constrain abundances of isotopes with weak observational limits. To push the limits and improve constraints on BBN models, uncertainties in key nuclear reaction rates must be minimized. To this end, we made new precise measurements of the d(d,p)t and d(d,n)^3He total cross sections at lab energies from 110 keV to 650 keV. A complete fit was performed in energy and angle to both angular distribution and normalization data for both reactions simultaneously. By including parameters for experimental variables in the fit, error correlations between detectors, reactions, and reaction energies were accurately tabulated by computational methods. With uncertainties around 2% +/- 1% scale error, these new measurements significantly improve on the existing data set. At relevant temperatures, using the data of the present work, both reaction rates are found to be about 7% higher than those in the widely used Nuclear Astrophysics Compilation of Reaction Rates (NACRE). These data will thus lead not only to reduced uncertainties, but also to modifications in the BBN abundance predictions.Comment: 15 pages, 11 figures, minor editorial change

Technology of dual-creative training highly skilled workers

The article is devoted to the technology of the integrated dual-creative training of highly skilled workers electrical profile.Статья посвящена технологии комплексной дуально-творческой подготовки рабочих высокой квалификации электротехнического профиля

Superior strength of carbon steel with an ultrafine-grained microstructure and its enhanced thermal stability

© 2015, Springer Science+Business Media New York. The paper presents the results of a study on the microstructure and mechanical properties of a medium-carbon steel (0.45 % C) processed by severe plastic deformation (SPD) via high-pressure torsion (HPT). Martensite quenching was first applied to the material, and then HPT processing was conducted at a temperature of 350 °C. As a result, a nanocomposite type microstructure is formed: an ultrafine-grained (UFG) ferrite matrix with fine cementite particles located predominantly at the boundaries of ferrite grains. The processed steel is characterized by a high-strength state, with an ultimate tensile strength over 2500 MPa. Special attention is given to analysis of the thermal stability of the microstructure and properties of the steel after HPT processing in comparison with quenching. It is shown that the thermal stability of the UFG structure produced by HPT is visibly higher than that of quenching-induced martensite. The origin of the enhanced strength and thermal stability of the UFG steel is discussed

Microstructure transformation in a cast Cu-Fe alloy at high pressure torsion deformation

© 2016 Advance Study Center Co. Ltd.The effect of high pressure torsion (HPT) on the microstructure of Cu-Fe 36 wt.% alloy has been studied. The initial Cu-Fe alloy has a dendritic structure, the length of dendrites is up to 100 μm. As a result of HPT (20 anvil revolutions at 400 °C) a nanostructural state is formed. The average size of the Cu and α-Fe grains is 60 and 35 nm correspondingly. The volume fraction of the Fe phase reduces from the initial 37% down to 15% after HPT. The concentration of iron dissolved in the copper lattice reaches 20%. The subsequent annealing at 700 °C for 1 hour results in some coarsening of α-Fe particles, as compared to the state after HPT. However, the typical dendritic structure of the cast alloy does not recover; it remains dispersed with the size of α-Fe particles less than 20 μm. As a result of HPT the alloy microhardness increased from 1800 to 4000 MPa. The subsequent annealing at T = 700 °C decreased the microhardness to 2700 MPa, but this value is 1.5 times higher than that in the initial as cast state

Времяпролетная масс-спектрометрия с импульсным тлеющим разрядом для прямого определения летучих органических соединений в воздухе, азоте и аргоне. Процессы ионизации летучих органических соединений

Determination of volatile organic compounds (VOCs) in various gases, including atmospheric and exhaled human air, is required to solve a wide range of environmental problems, control the composition of various gases and is increasingly used for diagnosis of various diseases. Lately, methods of soft ionization with minimal fragmentation of the components have been rapidly developed. In particular, our research group is developing an approach to direct analysis of mixtures of VOCs using time-of-flight pulsed glow discharge mass spectrometry. Previously, the effects of different gases and gas mixtures on ionization processes were not compared. Therefore, the ionization mechanisms of VOCs in argon, nitrogen, and air were investigated in the present work. Toluene, p-xylene, chlorobenzene and 1,2,4-trimethylbenzene were chosen as the model VOCs. Optimization of microsecond pulsed glow discharge parameters (period and duration of the discharge pulse, repelling pulse delay time and pressure in the discharge cell) for each compound and a gas mixture of several VOCs was carried out. The predominant ionization mechanisms are the formation of a VOC molecular ion by Penning ionization and the proton transfer reaction; their influence being different for various gases. It is shown that the use of argon even with a small addition of water leads to the predominance of the proton transfer reaction, whereas in nitrogen and air the Penning ionization predominates. The maximum VOC intensities were achieved in air, and the developed approach was tested under optimized conditions for the analysis of exhaled air and ambient air samples. Key words: Volatile organic compounds, ionization mechanism, glow discharge, mass spectrometry, breath analysis, air analysisОпределение летучих органических соединений (ЛОС) в различных газах, в том числе в атмосферном и выдыхаемом человеком воздухе, требуется для решения широкого круга экологических задач, контроля состава различных газов и все шире применяется для диагностики различных заболеваний. В последнее время быстро развиваются методы мягкой ионизации с минимальной фрагментацией компонентов. В частности, нашей научной группой развивается подход к прямому анализу смесей ЛОС с помощью времяпролетной масс-спектрометрии импульсного тлеющего разряда. Ранее не сравнивали влияние на процессы ионизации различных газов и газовых смесей. В связи с этим в настоящей работе исследованы механизмы ионизации ЛОС в аргоне, азоте и воздухе. В качестве модельных ЛОС выбраны толуол, п-ксилол, хлорбензол и 1,2,4-триметилбензол. Проведена оптимизация параметров микросекундного импульсного тлеющего разряда (период и длительность разрядного импульса, задержка выталкивающего импульса, давление в разрядной ячейке) для каждого соединения и газовой смеси нескольких ЛОС. Преобладающими механизмами ионизации являются образование молекулярного иона ЛОС с помощью Пеннинговской ионизации и реакция с переносом протона, при этом для разных газов их влияние различно. Показано, что использование аргона даже с небольшой добавкой воды приводит к преобладанию реакции переноса протона, тогда как в азоте и воздушной смеси преобладает Пеннинговская ионизация. В оптимизированных условиях в воздухе, для которого были достигнуты наибольшие интенсивности ЛОС, проведена апробация разработанного подхода для анализа выдыхаемого человеком  воздуха и проб атмосферного воздуха. Ключевые слова: летучие органические соединения, механизм ионизации, тлеющий разряд, масс-спектрометрия, анализ выдыхаемого воздуха, анализ воздух